Balanced valve cartridge

ABSTRACT

A pressure reducing valve including a balanced valve cartridge. The balanced valve cartridge has a retainer including a central bore. A valve seat and a valve plug are disposed within the central bore and cooperate to open and close the valve. A cap closes one end of the central bore, the cap including a blind bore for receiving a portion of the valve plug. Downstream fluid pressure is transmitted into the blind bore through a hollow portion of the valve plug, thus balancing the valve plug within the retainer.

FIELD OF DISCLOSURE

The disclosure generally relates to balanced pressure regulating valvesand specifically to a balanced valve cartridge that may be mounted intoa housing of a balanced or unbalanced pressure regulating valve body.

BACKGROUND OF THE DISCLOSURE

Pressure regulating valves are used in myriad industrial and residentialapplications for controlling the downstream pressure of a fluid. Forexample, in chemical processing plants or oil refineries, pressureregulating valves are used to manipulate a flowing fluid to compensatefor increases or decreases in demand, or other load disturbances, andthus keep the fluid pressure regulated. Similarly, pressure regulatingvalves may be used in plumbing fixtures to maintain a pre-determinedpressure of fluid that automatically adjusts to variations in demand,such as anti-scald valves in showers or faucets. By controllingdownstream pressure, pressure regulating valves compensate forvariations in downstream demand. For example, as downstream demandincreases, pressure regulating valves open to allow more fluid to flowthrough the pressure regulating valve, thus maintaining a relativelyconstant downstream pressure. On the other hand, as downstream demanddecreases, pressure regulating valves close to reduce the amount offluid flowing through the pressure regulating valve, again maintaining arelatively constant downstream pressure.

Pressure regulating valves can be categorized as either balanced orunbalanced. Unbalanced valves typically have high pressure inlet fluidon one side of the valve plug and lower pressure outlet fluid on theother side of the valve plug. Unbalanced valves suffer from anundesirable effect known as decaying inlet characteristic. The decayinginlet characteristic is a phenomenon in which an unbalanced valveexperiences an unintended increase in downstream pressure as theupstream pressure decreases. This effect is undesirable as most pressureregulating valves attempt to maintain a constant downstream pressure.Decaying inlet characteristic is caused by fluid forces on the highpressure side of the valve plug attempting to move the valve plug to aclosed position. As a result, the valve must have some mechanism tooppose this fluid force on the valve plug. Because the mechanism thatopposes the fluid force typically has a set point, the force generatedby such a mechanism is constant while the fluid force on the inlet sideof the valve plug may vary (e.g., due to a decreasing supply of inletfluid, or due to pressure variations upstream of the valve). Decayinginlet characteristic is particularly important to applications having alimited compressed fluid source, such as gas cylinders, tube trailers,or hydrils, because in such applications, there is a fixed supply ofinlet fluid and thus, the inlet fluid pressure decreases as the inletfluid supply decreases.

Unbalanced valves also suffer from damage that occurs to the valve seat.In unbalanced valves with high inlet pressures, the fluid pressureacting on large valve orifices can crush the valve seat. As a result,unbalanced valves are not ideal for high pressure, large orificeapplications.

One way to minimize the decaying inlet characteristic is to minimize thedifference between inlet and outlet pressure. Thus, multiple stageunbalanced pressure regulators, where each stage only reduces thepressure by a small amount, are less subject to the decaying inletpressure characteristic. Multi-stage unbalanced pressure regulators aretypically well suited for relatively low flow applications.

To address the decaying inlet characteristic in higher flowapplications, balanced pressure regulating valves were developed. In thebalanced valve, a portion of the downstream pressure is vented to act onan upstream portion of the valve plug. Thus, the valve plug is“balanced,” having the same fluid pressure act on both upstream anddownstream portions of the valve plug. In this way, the decaying inletcharacteristic is eliminated (or greatly reduced) because there is nodifference in the fluid forces acting on valve plug surfaces bothupstream and downstream of the valve seat that would tend to force thevalve plug towards the closed position. In other words, the valve plugitself generates very little, or no opening/closing forces due to fluidpressures.

Recently, some unbalanced pressure reducing valves have been developedthat include a valve cartridge. The valve cartridge may be assembled asa sub-assembly. The valve cartridge may then be installed into anunbalanced valve body as a unit. Some unbalanced valve cartridgesinclude a valve plug, a valve seat, a retaining body, and a filter onthe high pressure side of the valve plug. Because fluid flowing throughthe unbalanced cartridge is filtered the life of the unbalanced valvecartridge may be extended and reliability and precision of theunbalanced pressure regulating valve may be improved. While such valvecartridges have improved assembly and durability, these valve cartridgeshave been limited to unbalanced pressure reducing valves due tomanufacturing and cost limitations.

SUMMARY

A pressure reducing valve includes a balanced valve cartridge. Thebalanced valve cartridge has a retainer including a central bore. Avalve seat and a valve plug are disposed within the central bore andcooperate to open and close the valve. A cap closes one end of thecentral bore, the cap includes a blind bore for receiving a portion ofthe valve plug. Downstream fluid pressure is transmitted into the blindbore through a hollow portion of the valve plug, thus balancing thevalve plug within the retainer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a pressure reducing valve having abalanced valve cartridge constructed in accordance with the teachings ofthe disclosure;

FIG. 2 is an enlarged cross-sectional view of the balanced valvecartridge of FIG. 1; and

FIG. 3 is a cross-sectional view of an alternate embodiment of abalanced valve cartridge constructed in accordance with the teachings ofthe disclosure.

While the disclosure is susceptible to various modifications andalternative constructions, certain illustrative embodiments thereof havebeen shown in the drawings and will be described below in detail. Itshould be understood, however, that there is no intention to limit thedisclosure to the specific forms disclosed, but on the contrary, theintention is to cover all modifications, alternative constructions, andequivalents falling within the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring now to the drawings and with specific reference to FIG. 1, apressure regulating valve is generally referred to by reference numeral20. The pressure regulating valve 20 includes a valve body 22 having afluid inlet 24 and a fluid outlet 26. The valve body 22 may in oneembodiment be capable of housing a typical unbalanced valve cartridge(not shown). A bonnet 28 houses a load spring 30 and a set pointadjusting mechanism 32. A balanced valve cartridge 40 is located withinthe valve body 22 between the fluid inlet 24 and the fluid outlet 26 toregulate downstream fluid pressure.

The valve 20 includes a diaphragm 50 that is responsive to downstreampressure in chamber 52. The diaphragm 50 is movable within the bonnet28. The diaphragm 50 is movable up and down in FIG. 1 and is located ata position in which force on the diaphragm 50 generated by the outletfluid pressure in chamber 52 is balanced with a force on the diaphragmgenerated by the load spring 30. The diaphragm 50 may be supportedand/or reinforced by a diaphragm plate 54. The diaphragm plate 54 bothsupports the diaphragm 50 and acts as a force transfer mechanism totransfer force from the load spring 30 to the diaphragm 50. The loadspring 30 seats between the diaphragm plate 54 and a spring button 56.An adjustment screw 58 is disposed in an opening 60 in the bonnet 28.The adjustment screw 58 is displaceable within the opening 60 so thatone end of the adjustment screw 58 abuts against the spring button 56.Movement of the adjustment screw changes a location of the spring button56 within the bonnet 28 and thus, the spring force acting on thediaphragm plate 54 from the load spring 30 may be modified. In this way,a set point of the pressure reducing valve 20 may be adjusted.

To facilitate adjustment of the adjustment screw 58, the adjustmentscrew 58 may be connected to a hand knob 61 by a hand knob insert 62,and a nut 64. Access to the nut 64 may be available through an opening66 in the hand knob 61, which may be covered by a hole plug 68.

As seen in FIG. 2, the balanced valve cartridge 40 includes a retainer70 having a fluid inlet 72, a fluid outlet 74, and a central bore 75having a first end 77 and a second end 79. The retainer 70 may includean opening 76 opposite the fluid outlet 74. A cap 78 may close (andoptionally seal) the opening 76. The cap 78 may include a blind bore 80opening towards the fluid outlet 74. The cap 78 may also include athreaded portion 82 that cooperates with a threaded portion 83 on aninner surface of the retainer 70 to secure the cap 78 over the opening76. Alternatively, the cap 78 may be crimped onto the retainer 70.

A valve seat 84 may be disposed within the retainer 70 proximate thefluid outlet 74. A valve plug 86 is disposed within the retainer 70 andthe valve plug 86 is movable within the central bore 75 of the retainer70 to cooperate with the valve seat 84 to regulate fluid flow throughfluid outlet 74. The valve plug 86 includes a stem portion 88 thatcooperates with the diaphragm 50 (FIG. 1) to position the valve plug 86within the retainer 70. A spring 90 is located between the valve plug 86and the cap 78 to bias the valve plug 86 towards a closed position.Optionally, a washer 92 may be disposed against the cap 78 to act as aseat for one end of the spring 90 and to protect and retain one or moreseals 102. An opposite end of the spring 90 may seat against the valveplug 86 at a shoulder 94 of the valve plug 86. The valve plug 86 mayinclude a hollow center portion 96 and an angled vent portion 98. Theangled vent portion 98 has an inlet on the downstream side of the valveseat 84 and an outlet connected to the hollow center portion 96. Thehollow center portion 96, in turn, has an inlet connected to the outletof the angled vent portion 98, and an outlet that vents downstream valvepressure into a void 100 located between the valve plug 86 and the cap78. The angled vent portion 98 and the hollow center portion 96cooperate to allow downstream pressure into the void 100 in the cap 78created by the blind bore 80 and the valve plug 86. In this way, thevalve plug 86 becomes a balanced valve plug, thus reducing oreliminating decaying inlet characteristic and reducing force on thevalve seat 84 due to inlet pressure.

The void 100 may be sealed from inlet pressure by the one or more seals102, such as o-rings, disposed within an annular recess 103 in the blindbore 80. Likewise, the retainer 70 may be sealed against the valve bodyby one or more seals 104, such as o-rings. Of course, any other type ofknown seal may be used depending on the use and requirements of thevalve 20.

A sealing means, such as a filter 110 may be disposed within theretainer 70 between an inner surface of the retainer 70 and the valveplug 86. The filter 110 may be secured in the retainer 70 between thecap 78 and the valve seat 84. An inner surface of the retainer 70 mayinclude a first portion 120 and a second portion 122. The first portion120 may have a smaller diameter than the second portion 122 so that agap 124 is created between the filter 110 and the second portion 122,while the filter 110 is held in place laterally by the first portion120. The gap 124 may allow fluid to flow lengthwise along the filter110, thus making a larger portion of the filter 110 available for fluidto flow through. As a result, the valve plug 86, valve seat 84, andspring 90 are all protected from contaminants and impurities by thefilter 110. This feature increases the life expectancy and precision ofthe pressure reducing valve 20.

The filter 110 also compresses and seals the valve seat 84 against theinner surface of the retainer 70. As a result, inlet fluid pressure isprevented from passing the valve seat 84 between the valve seat 84 andthe retainer 70. Other means of sealing the valve seat 84 with theretainer 70 are possible including, but not limited to, using a separatepart (not shown) to apply a sealing force to the valve seat 84, andinstalling a seat retainer (not shown) between the valve seat 84 and theretainer 70.

In an alternate embodiment shown in FIG. 3, the valve plug 86 includes ahollow stem 88. The stem 88 also may include an opening 89. Outlet fluidpressure may be transmitted through the opening 89 and into the hollowstem 88 and finally through the valve plug 86 into the void 100.

As opposed to prior art unbalanced valve cartridges, the balanced valvecartridge of the present disclosure may be installed in a typicalunbalanced valve body. Thus, manufacturing and logistic efficiency isimproved because a single valve body may be changed from an unbalancedvalve to a balanced valve simply by changing the valve cartridge.

In one embodiment, an unbalanced pressure regulating valve may beconverted to a balanced pressure regulating valve by 1) removing anunbalanced valve cartridge from a valve body, and 2) inserting abalanced valve cartridge according to the disclosure within the valvebody.

From the forgoing, one of ordinary skill in the art will readilyunderstand that through the teachings of the disclosure, a pressurereducing valve can be constructed having a removable balanced valvecartridge. Moreover, a pressure reducing valve may be changed from anunbalanced valve to a balanced valve quickly and easily.

What is claimed is: 1-16. (canceled)
 17. A method of converting anunbalanced valve to a balanced valve, the method comprising: obtainingan unbalanced valve comprising a valve body and an unbalanced valvecartridge; providing a balanced valve cartridge comprising: a retainerhaving a central bore including a first end and a second end, an innersurface, and at least one opening in the inner surface forming a fluidinlet; a valve seat disposed within the central bore proximate the firstend of the central bore; a movable valve plug at least partiallydisposed within the central bore, the movable valve plug selectivelyopening and closing the first end of the central bore by sliding withinthe central bore to cooperate with the valve seat, the movable valveplug having a hollow center portion; a sealing means disposed within thecentral bore between the inner surface of the central bore and the valveplug; and an end cap disposed at the second end of the central bore, theend cap closing the second end of the central bore, the end capincluding a blind bore facing the valve plug, the blind bore receivingone end of the valve plug so that the blind bore is fluidly connected toa downstream side of the valve seat by the hollow center portion of thevalve plug; wherein the end cap plugs the second end of the central boreand traps the filter against the valve seat, thereby fixing the filterwithin the central bore and trapping the filter and valve plug betweenthe end cap and the retainer; removing the unbalanced valve cartridgefrom the valve body; and inserting the balanced valve cartridge into thevalve body.
 18. The method of claim 17, wherein the step of insertingthe balanced valve cartridge includes threading the outer surface of theend cap into the retainer.
 19. The method of claim 17, furthercomprising the step of venting downstream pressure through the hollowcenter portion of the movable valve plug and into the blind bore of theend cap.
 20. The method of claim 17, further comprising the step ofsealing the annular bore by disposing a seal within an annular recessnear an open end of the blind bore.
 21. The method of claim 17, whereinthe balanced valve cartridge comprises a spring trapped between the endcap and the valve plug, the spring biasing the valve plug towards thevalve seat.
 22. The method of claim 21, wherein a washer is disposedbetween the spring and the end cap.
 23. The method of claim 17, whereinthe blind bore includes an annular recess near an open end of the blindbore.
 24. The method of claim 23, wherein a seal is disposed in theannular recess, the seal being trapped between the end cap and the valveplug.
 25. The method of claim 17, wherein an outer surface of the endcap includes a threaded portion and the inner surface of the retainerincludes a threaded portion, the threaded portion of the end cap and thethreaded portion of the retainer cooperating to attach the end cap tothe retainer.
 26. The method of claim 17, wherein a valve stem isattached to first end of the valve plug, the valve stem extending out ofthe first end of the central bore on a downstream side of the valveseat.
 27. The method of claim 26, wherein the hollow center portion ofthe valve plug extends into the valve stem.
 28. The method of claim 17,wherein the hollow center portion of the valve plug is connected with anangled relief portion, the angled relief portion and the hollow centerportion cooperating to fluidly connect the blind bore and a downstreamside of the valve seat.
 29. The method of claim 17, wherein the innersurface of the central bore includes a first portion and a secondportion, wherein the first portion has a smaller diameter than thesecond portion.
 30. The method of claim 29, wherein the sealing means isdisposed immediately adjacent the first portion of the inner surface ofthe central bore and the second portion of the inner surface of thecentral bore forms an annular space between the filter and the innersurface of the central bore.